mpg on 04 sierra

hi, have a 04 sierra 1500 4x4 extended cab with the 5.3. notice the fuel mileage seems to go down in winter with heat on(14). seems if i turn off heat it
gets a little better. in warm months it gets better mileage.(16)\, except when i use the ac. took 800 mile trip south mid november and averaged close to 19.
plugs and wires (mallory) done about a year ago,new air filter 1 month ago. don't drive it hard, i keep my foot out of it as much as i can, but cold seems to make it worse. thanks, any help would be appreciated.:neutral:
dave

p.s. any ideas on where to get some performance parts for engine(cam,lifters, comp.chip):gasp:

I have noticed the same affects with my 04 Silverado but I have noticed a decline in mpg's regardless of whether the heat is on or not. Summitracing.com has lots of good stuff for these trucks along with jegs racing and these are very popular motors so parts aren't stupid expensive.

L33....The Vortec 5300 L33 (VIN code "B") is an Aluminum Block Version of the LM7, and was referred to as the Vortec 5300 HO in marketing materials. How ever it should be noted that the L33 uses a flat top piston from the 4.8L instead of the standard dish piston found in the LM7

thanks.. what about a cold air intake, always heard that they are worse because they suck in the hot air from the engine
thanks,
dave

Click to expand...

If you're getting hot air from the engine bay, it's not a cold air intake. The factory intake setup is cold air. It draws in air from the fender well, not the engine bay. The main problem with the factory intake setup is the intake tube between the filter housing and the throttle body. But changing it isn't going to give you any real MPG boost. You might get 1 MPG if you're extremely lucky with it.

There isn't really a one performance part under $800 that's going to give you huge gains in the HP, Torque, and MPG categories. You have to get a set up like a new intake tube/filter then maybe and exhaust and then a custom tune. When you put at least two of those three together you'll start seeing gains. I went with the intake tube/filter with a custom tune from BlackBear and they have helped a lot